1. Field of the Invention
This invention relates to novel compounds which belong to pyrone-3-carboxamide compounds, particularly 2,6-dimethyl-4-oxo-4H-pyran-3-carboxamides. The compounds of this invention show a growth inhibitory activity on plants and also are useful as intermediates for preparing medicines or agricultural chemicals.
2. Description of the Prior Art
Certain compounds belonging to 2,6-dimethyl-4-oxo-4H-pyran-3-carboxamides have been mentioned in the literature.
That is, it has been known that the treatment of o-haloacetoanilides (2-chloro, 2-bromo, 2,4-dichloro or 2,5-dichloro compounds) with polyphosphoric acid for an hour at 140.degree. C. gave the corresponding halogen derivatives of 2,6-dimethyl-4-oxo-N-phenyl-4H-pyran-3-carboxamide (A. K. Mallams & S. S. Islaelstam: J. Org. Chem., 29, 3548(1964); A. K. Mallams: J. Org. Chem., 29, 3555(1964). This method using polyphosphoric acid was applied to other acetoacetoanilides (2-fluoro, 2-piperidino, 2-hexahydroazepinyl, 2-morpholino, 2-pyrrolidinyl or the like) to yield the corresponding 2,6-dimethyl-4-oxo-4H-pyran-3-carboxamide compounds [R. Garner & H. Suschitzky: J. Chem. Soc. (C), 186(1966)].
The formation of 2,6-dimethyl-N-(4-nitrophenyl)-4-oxo-4H-pyran-3-carboxamide was identified as the reaction product of p-nitroaniline and diketene [Kato & Kubota: Yakugakuzassi, 87, 1212(1967)]. Also, N-(2-chlorophenyl)-2,6-dimethyl-4-oxo-4H-pyran-3-carboxamide was obtained by treating 2,6-dimethyl-4-oxo-4H-pyran-3-carboxylic acid with thionyl chloride followed by the reaction with o-chloroaniline, or heating the p-nitrophenyl ester of 2,6-dimethyl-4-oxo-4H-pyran-3-carboxylic acid and o-chloroaniline for 4.3 hours at 110.degree. C. [Toda: Yakugakuzassi, 87, 1351(1967)]. This reference discloses pyrone-3-carboxamide compounds which were obtained by the reaction of 4-aminotropolones with diketene.
Also, Japanese Patent Publication No. 45(1970)-31663 discloses a process for preparing 2,6-dimethyl-4-oxo-4H-pyran-3-carboxamides which comprises reacting isocyanates and diketene in the presence of an acid catalyst. In the examples this publication describes 2,6-dimethyl-4-oxo-N-phenyl-4H-pyran-3-carboxamide, 2,6-dimethyl-N-(2-methylphenyl)-4-oxo-4H-pyran-3-carboxamide, N-(2-chlorophenyl)-2,6-dimethyl-4-oxo-4H-pyran-3-carboxamide, 2,6-dimethyl-N-(2-nitrophenyl)-4-oxo-4H-pyran-3-carboxamide, N-(2,5-dichlorophenyl)-2,6-dimethyl-4-oxo-4H-pyran-3-carboxamide, oxo-4H-2,6-dimethyl-N-(3-nitrophenyl)-4-oxo-4H-pyran-3-carboxamide and 2,6-dimethyl-N-(4-methylphenyl)-4-oxo-4H-pyran-3-carboxamide.
Further, 2,6-dimethyl-4-oxo-N-phenyl-4H-pyran-3-carboxamide, N-(4-methoxyphenyl)-2,6-dimethyl-4-oxo-4H-pyran-3-carboxamide and N-(4-chlorophenyl)-2,6-dimethyl-4-oxo-4H-pyran-3-carboxamide have been disclosed as the reaction products of 3-morpholinocrotonanilide compounds and diketene [Kato et al: Yakugakuzassi, 101, 43(1981)].
There have also been references to pyrone-3-carboxamide compounds which correspond to aminotropones (H. Toda & S. Seto: Chem. Pharm. Bull., 19, 1477(1971), aminopyridines (T. Kato et al: Chem. Pharm. Bull., 20, 133(1972); ibid. 28, 2129(1980); H. L. Yale et al: J. Heterocyclic Chem., 14, 637(1977) and 2-amino-1,3,4-thiadiazoles (R. F. Lauer et al: J. Heterocyclic Chem., 13, 291(1976), respectively.
The above mentioned Japanese Patent Publication No. 45(1970)-31663 discloses that 2,6-dimethyl-4-oxo-4H-pyran-3-carboxamides have utility as agricultural drugs such as control agents of sheath blight of rice, nematocides, or acaricides, or drugs such as antiviral agents or the like, but does not disclose any data supporting such utility.
As discussed above, there were no reports on the pyrone-3-carboxamide compounds represented by formula (I) of the present invention, together with no suggestion on their plant growth inhibitory activity.